Fishing lures having various mechanisms which may be manipulated to select one of two modes of operation are known in the art. In one such mode of operation, the lure will remain on or near the surface of the water when trolling and in the other mode of operation the lure will dive below the surface.
Such fishing lures fall into two distinct categories of structure. The first catagory includes a single piece construction of the body of the lure so that to effect one of the two modes of operation, the hook and fishing line must be attached to specific places on the body of the lure. With this type construction, when one wishes to change the mode of operation the fishing line and hook must be removed and reattached.
The other catagory includes lures having bodies which are composed of two or more parts held together by various combinations of springs, pins, washers, and screws or clips.
Such structures as are known add significantly to their cost of manufacture. Worse they detract from their reliability due to the usual complexity and number of interacting parts.
Fish feed at different depths as a function of food availability, water temperature, salinity, and a variety of environmental factors. This necessitates that a successful fisherman present his bait to the fish at the depth at which they are currently feeding. This is not always possible when artificial baits are used because the artificial bait or lure, which has the most appealing motion through the water for the particular species of fish being sought, may not operate properly at the depth at which the fish are swimming.
Artificial baits or fishing lures used for trolling, casting, or jigging are normally designed to operate at predetermined depths.
The depth of operation of a fishing lure is normally the function of the density of the lure assembly, its hydrodynamic shape and speed of motion.
Lure density and shape are usually fixed during manufacture so that the depth, at which it operates properly, is fixed so that the fisherman cannot vary the operating depth of a lure to place the lure at the same depth as the fish.
In some cases, a lure may be made to dive deeper or shallower by varying the retrieval rate but the shape of a lure dictates that it should be retrieved or trolled at a set speed to achieve the most lifelike action.
Thus, the successful fisherman has to carry a variety of lures designed to operate at various depths at which fish may be found. In many cases, a lure having the proper motion through the water does not have the proper density and, therefore, the lure which should be most successful in attracting fish fails to reach them.
It is accepted practice in the sport of fishing to employ a plurality of rods and reels for successful fishing, each with a different lure, the rationale being that when a fish strikes and misses one lure, the chance is increased that that fish will not strike that lure again, at least immediately.
Ergo the option afforded the fisherman to select a different lure on a different setup, all in the effort to persuade the fish to strike anew. At least there is a certain mental balm for the fisherman in believing that such a system works.
Experience has shown that where a fish, let us say a bass, strikes at a surface lure and misses, the bass will normally head for or more in the direction of the water's bottom.
Were the fisherman to reel in the surface lure quickly and to cast out a crank bait or a jig bait to the area where the bass is believed to have moved, there is an improved opportunity for catching same.